Dolphins sing 'Batman' theme

Dolphins are the only mammals other than humans to recognise rhythms and reproduce them vocally (Image: iStockphoto)

Scientists have taught dolphins to combine both rhythm and vocalisations to produce music, resulting in an extremely high-pitched, short version of the Batman theme song.

The findings, outlined in two studies, are the first time that nonhuman mammals have demonstrated they can recognise rhythms and reproduce them vocally.

"Humans are sensitive to rhythms embedded in sequences of sounds, but we typically consider this skill to be part of processing for language and music, cognitive domains that we consider to be uniquely human," says Professor Heidi Harley, lead author of both studies.

Harley, who is associate professor of social sciences at the New College of Florida in Sarasota, says that both studies tested dolphins at Disney's Epcot Center in Florida.

The researchers first had an adult male bottlenose dolphin position itself in front of an underwater sound projector, called a hydrophone, that produced six different 14 kiloherz, 4 second rhythms.

The dolphin was rewarded for performing a certain behaviour to each rhythm. For example, when rhythm 1 played, it waved its pectoral fin and when rhythm 2 played, it tossed a ball.

The various rhythms were played at different frequencies and tempos to ensure the dolphin was recognising rhythms instead of just frequencies or sound durations.

Another adult male was trained to produce similar rhythms using a pneumatic switch, essentially a small, air-filled ball connected to a computer that then generated sounds whenever the dolphin pressed the switch.

"The dolphin was reinforced for producing a specific rhythm to a specific object," says Harley.

"For example, when we presented him with a Batman doll, he received a fish for producing a specific rhythm, in this case, a short sound and then a long one."

"If you recall the original Batman TV series musical intro you'll probably remember the way they sang 'Bat-maaaaaaaan'," she adds.

The dolphin spontaneously vocalised to the rhythms, so the researchers started to reward the male with fish whenever it matched its 'singing' to the rhythms.

By the end of the studies, the scientists could show an object, such as the Batman doll, which represented a certain rhythm-vocalisation combo to the dolphin, and it would create the correct sounds both vocally and using the switch.

Batmaaaaaaan

Gordon Bauer, associate professor of psychology at the New College of Florida who did not work on the studies, says, "This is the first report, to my knowledge, of a nonhuman mammal's ability to discriminate rhythmic patterns."

But Bauer doubts that dolphins realise they are producing what people consider 'music'.

"I think music is a human construct," he says. "I doubt that it has pertinence to animals, although the elements of music, such as pitch, time, timbre, rhythm, etc, may be incorporated into animal communication."

Harley agrees, and hopes the everyday vocalisations of dolphins will be analysed in terms of their rhythmic content.

In the near future, she and her team are planning to test the dolphins on their ability to recognise recordings of their own rhythms by having them associate their own sound creations with identifying objects similar to the Batman doll.